1. Technical Field
The present invention relates to a battery charger.
2. Discussion of the Related Art
Nowadays mobile phones, digital cameras, notebooks, netbooks, tablets etc. have become daily used electronic devices. The power of the batteries of these electronic devices determines a length of time of use of the electronic device. Electronic devices such as mobile phones, digital cameras, notebooks, netbooks, tablets etc. should be used with corresponding battery chargers. Generally, these battery chargers (or called as power supplies) are unique to the corresponding electronic devices.
Typically, each battery charger is provided with an input terminal, such as a USB terminal, for connection to the power line for charging the battery and simultaneously powering the device connected to the battery, as shown in FIG. 1.
The battery charger 20 in FIG. 1 comprises the USB input terminal IN, a control block 10 configured to control first M1 and second M2 transistors arranged in the path between the input terminal IN and the output terminals SYS and Ld and third M3 and fourth M4 transistors arranged in the path between the input terminal IN and the battery BAT downstream the transistors M1, M2. When a supply voltage is present at the input terminal IN, the control block 10 turns on the transistors M1-M4 to provide power to the loads connected to the terminals SYS and Ld and to charge the battery BAT. When the supply voltage is not present at the input terminal IN, the control block 10 turns on the transistors M3-M4 and turns off M1-M2 so the power deriving from the battery BAT supplies the loads connected to the terminals SYS and Ld and the battery charger itself.
The control block receives an enable signal CEN an a shut-down signal SD and comprises a current modulation block adapted to control the transistor M4. Also the control block 10 is able to send an enable signal EN to a LDO block configured to supply an external load with a constant voltage by means of the output terminal Ld.
Also the battery charger comprises some protection circuits to operate the battery disconnection when a protection parameter such as the over discharge current (OCD) or the over discharge voltage (OVD) happens. For the continuous monitoring of the protection parameters the battery charger may consume a certain quantity of current, for example up to 15 microampere, which can be considered high in the case wherein a load, for example a microcontroller, connected with the battery charger has the same current consumption.